Mycorrhizal Root Colonization Research Articles

The Effect of Combined Application of Biocontrol Microorganisms and Arbuscular Mycorrhizal Fungi on Plant Growth and Yield of Tomato (Solanum lycopersicum L.)

Sustainable plant production requires less use of synthetic chemicals in plant nutrition and protection. Microbial products are among the most promising substitutes for chemicals. With the increasing popularity and availability of such products, it has become obligatory to use different microbes together. The effect of this has been tested in several studies, but their results have sometimes been contradictory depending on the microbial strains tested and the mode of application. We tested the effect of two commercially available antagonists and Funneliformis mosseae alone and in combination on tomato. Mycorrhizal treatment increased plant growth and yield, both alone and combined with the antagonists; however, mycorrhizal root colonization was not influenced by the antagonist. This treatment also led to a slight decrease in the occurrence of Trichoderma spp. on tomato roots but did not impede the colonization of roots by the applied Trichoderma strain. Our result confirmed that Trichoderma asperellum (T34) and Streptomyces griseoviridis (K61) can be safely combined with arbuscular mycorrhizal fungi (AMF), namely with F. mosseae.

Improved Waterlogging Tolerance in Roots of Cucumber Plants after Inoculation with Arbuscular Mycorrhizal Fungi

Mycorrhizal symbiosis enhances host plant resistance to various unfavorable environmental stresses, but whether and how it also enhances waterlogging tolerance in cucumber plants is not known. The objective of this study was to analyze the effect of Paraglomus occultum inoculation on biomass production, osmolyte levels, and the expression of 12 heat shock protein 70 (Hsp70) genes and 14 plasma membrane intrinsic protein (PIP) genes in the roots of cucumber plants under a short-term waterlogging stress (WS) (5 days) condition. Although the short-term WS treatment significantly inhibited the arbuscular mycorrhizal fungal colonization of roots, the inoculation with arbuscular mycorrhizal fungi (AMFs) significantly increased leaf, stem, and root biomass under WS. AMF inoculation also significantly increased root glucose, sucrose, betaine, and proline contents, along with decreased fructose levels, compared with the uninoculated control. More CsHsp70 and CsPIP genes were up-regulated in AMF-inoculated plants than in AMF-uninoculated plants in response to WS. AMF inoculation showed no significant effect on the expression of any of the examined CsHsp70 genes under no-waterlogging stress, but it did raise the expression of 11 of 12 CsHsp70 genes under WS. AMF colonization also down-regulated or had no effect on CsPIP expression under no-waterlogging stress, whereas it up-regulated the expression of 12 of the 14 CsPIP genes under WS. It is concluded that AMF inoculation enhances waterlogging tolerance in cucumber plants by increasing osmolyte levels and stress-responsive gene (CsPIP and CsHsp70) expression.

Arbuscular mycorrhizal fungi improve the competitive advantage of a native plant relative to a congeneric invasive plant in growth and nutrition.

Plant invasions severely threaten natural ecosystems, and invasive plants often outcompete native plants across various ecosystems. Arbuscular mycorrhizal (AM) fungi, serving as beneficial microorganisms for host plants, can greatly influence the competitive outcomes of invasive plants against native plants. However, it remains unclear how AM fungi alter the competitive balance between native and invasive species. A competitive experiment was conducted using an invasive Eupatorium adenophorum paired with a native congener Eupatorium lindleyanum. Specifically, both species were inoculated with (M+) or without (M-) the fungus Glomus etunicatum under intraspecific (Intra-) and interspecific (Inter-) competition. Plant traits were measured and analyzed regarding the growth and nutrition of both species. The results exhibited that the AM fungus significantly increased the height, diameter, biomass, C, N, and P acquisition of both the invasive E. adenophorum and the native E. lindleyanum. The root mycorrhizal colonization and the mycorrhizal dependency of native E. lindleyanum were greater than those of invasive E. adenophorum. Under M+, the Inter-competition inhibited the growth and nutrition of invasive E. adenophorum compared to the Intra- competition. Further, native E. lindleyanum exhibited higher competitiveness than invasive E. adenophorum in growth and nutrition. Meanwhile, the AM fungus significantly improved the competitiveness of native E. lindleyanum over invasive E. adenophorum. In conclusion, AM fungus improved the competitive advantage of native E. lindleyanum over invasive E. adenophorum in growth and nutrition, potentially contributing to native species competitively resisting the invasion of exotic species. These findings emphasize the importance of AM fungi in helping native plants resist the invasion of exotic plants and further contribute to understanding plant invasion prevention mechanisms.

Potencial Simbiótico de Microrganismos do Solo na Promoção do Crescimento de Espécies Arbóreas da Mata Atlântica

The objective of this study was to evaluate the potential of topsoil obtained from a natural forest fragment in the Brazilian Atlantic Forest to serve as a source of symbiotic microorganisms capable of promoting the growth of native tree species in ecological restoration projects. In greenhouse conditions, 14 experiments in a completely randomized design were conducted in 1,700 cm³ pots filled with sterilized substrate. The effect of adding 80 g of topsoil, either in natura or sterilized, to the substrate was tested on the growth of 14 tree species. Plant height, stem diameter, mycorrhizal colonization and dry masses of shoot, roots, and nodules of tree species were measured. Applying the topsoil to the pots generally resulted in significant increases in height and stem diameter of seedlings compared to the control group during the four to six-month evaluation period. This effect was particularly greater in the nodulating species Plathymenia reticulata, Dalbergia nigra and Mimosa bimucronata, with increases in height and stem diameter of up to 328% and 484%, respectively. Forest topsoil also had a positive impact on the growth of shoot, roots, and nodules of the plants, significantly differing from the control groups. Only the plants that received the topsoil in natura exhibited mycorrhizal colonization and the formation of nodules in nitrogen-fixing species. These plants that established mycorrhizas and nodules presented higher concentrations of phosphorous and nitrogen in their biomass, respectively. Under controlled conditions, the use of forest topsoil proved to be a promising strategy for the introduction of microorganisms that can enhance the growth of tree species, thereby holding potential for implementation in nurseries and field settings.
 

Plant functional traits couple with range size and shape in European trees

AbstractAimPlant functional traits are frequently proposed as influential factors in species distribution. However, there is a gap in assessing how plant resource‐economic traits relate to the size and shape of a species' geographical range, and to what extent these relationships are conserved over evolutionary history. Specifically, an acquisitive strategy (characterized by heightened metabolism, shorter lifespan and quicker generation turnover) may promote isotropic range formations, resulting in less elongated and larger ranges. Here, I tested this link using data from 98 native European tree species.LocationPalaearctic.Time periodPresent.Major taxa studiedTrees.MethodsI used chorological maps to quantify two independent range attributes: species' range area and elongation. I considered 28 functional traits linked to resource‐use strategy measured in above‐ and below‐ground organs. I used multi‐response phylogenetic mixed models to calculate the conservative trait correlation (CTC) and the phylogenetically independent correlation (IND) component of each functional trait with range area and elongation.ResultsRange area positively correlated with resource acquisitive strategies, while range elongation correlated with resource conservative strategies. This pattern was consistent across the examined traits but statistically significant in seven out of the 28 traits, including specific leaf area, specific root area and root mycorrhizal colonization. Traits related to leaf and root nutritional status exhibited the weakest relationships with range attributes. Significant correlations were more frequent in the IND component and often showed contrasting trends compared to CTC.Main conclusionsPlant resource‐use strategy emerges as a relevant factor to gain insights on what shapes species' geographical distribution, alongside more established drivers such as dispersal limitation and climatic tolerance. Trait‐range relationships are driven by processes leaving a weak phylogenetic signature. These processes may result from direct selection, where functional traits impact range attributes, or indirect effects, such as the co‐variation of ranges and traits with environmental niche optima.

Arbuscular mycorrhizal fungi and rhizobia accelerate plant growth and N accumulation and contribution to soil total N in white clover by difficultly extractable glomalin-related soil protein

Arbuscular mycorrhizal fungi and rhizobia are soil symbiotic microorganisms involved in plant nitrogen (N) acquisition, whereas it is unclear how single or combined inoculation of both contributes to soil total N in legume crops. This study analyzed the effects of single or combined inoculation with arbuscular mycorrhizal fungus (Paraglomus occultum) and rhizobium (Rhizobium leguminosarum bv. trifolii) on growth performance, root soluble protein, leghemoglobin, NH4+-N, NO3−-N, and N concentrations, nitrogenase activities, soil total N contents, N contents in glomalin-related soil protein (GRSP), as well as the contribution of N in GRSP to soil total N in white clover. Twelve weeks after inoculation, P. occultum promoted nodule formation, and R. leguminosarum bv. trifolii accelerated root mycorrhizal colonization. Single or combined inoculation with P. occultum and R. leguminosarum bv. trifolii improved biomass, root total length, surface area and volume, root soluble protein concentrations, nodule leghemoglobin concentrations, and nitrogenase activities to varying degrees, with the trend of improvement being more pronounced with combined inoculation. R. leguminosarum bv. trifolii and/or P. occultum significantly increased NO3−-N, NH4+-N, and total N concentrations in nodules and roots, as well as soil total N concentrations. The N in easily extractable GRSP (EE-GRSP) and difficultly extractable GRSP (DE-GRSP) was 4.37–5.64 mg/g and 6.69–7.83 mg/g, respectively, contributing 2.68–3.26 % and 2.28–3.10 % of soil total N. P. occultum and combined inoculation accelerated the production of EE-GRSP and DE-GRSP and N in EE-GRSP. R. leguminosarum bv. trifolii not only significantly increased DE-GRSP production but also reduced N in DE-GRSP. R. leguminosarum bv. trifolii or P. occultum significantly increased the contribution of N in DE-GRSP, not EE-GRSP, to soil total N. It was concluded that arbuscular mycorrhizal fungus and rhizobium accelerated N accumulation and contribution to soil total N in white clover by DE-GRSP.

Effect of Cinnamon Leaf Compost on Selected Soil Properties in Cinnamon (Cinnamomum zeylanicum Blume) Growing Soils

Integrated nutrient-management programs incorporating organic and inorganic fertilizers have been suggested to increase crop yields and reduce adverse environmental impacts in intensive agriculture. This study was conducted to investigate the effect of long-term cinnamon leaf compost (CLC) application on some selected physical, biological and chemical soil properties and the horizontal and vertical distribution of some selected soil properties in cinnamon-growing soils. The study was conducted in the National Cinnamon Research and Training Center, Palolpitiya, from January to April 2022. The experimental design was Randomized Complete Block Design (RCBD) with six treatments (T1-Control, T2-Current recommendation (CR), T3-3/4 CR with 5 t/ha/yr CLC, T4-1/2 CR with 10 t/ha/yr CLC, T5-1/4 CR with 15 t/ha/yr CLC, T6-20 t/ha/yr CLC) and three replicates. Soil samples were collected considering three horizontal distances (15, 30 and 45 cm) and with three depths (10, 20 and 30 cm). Soil physical properties (aggregate stability, bulk density, soil moisture), chemical properties (soil organic carbon (SOC), pH, electrical conductivity (EC)), and biological properties (arbuscular mycorrhizal root colonization) were determined. Water stable aggregate (WSA), SOC, and soil pH were significantly affected by the treatments, and all the variables except EC were significantly affected by the soil depth (p<0.05). Soil pH was the only variable that was significantly affected by the horizontal distance (p<0.05). Only SOC and pH have shown a significant interaction effect among treatments and depth. The application of CLC (20 t/ha/yr) significantly increases the WSA and SOC. Arbuscular mycorrhizal fungi root colonization was increased with the incorporation of CLC. Continuous application of inorganic fertilizers (T2) caused soil compaction and acidification. WSA, soil pH, and SOC were significantly improved within the 0-10 cm soil depth. The best performances of WSA, pH, and EC were shown in 30-45 cm and SOC in 15–30 cm horizontal distance from the plant base and 0-10 cm soil depth with the application of 1/2 CR and 10 t/ha/yr CLC comparison to other fertilizer combinations. 
 Keywords: Aggregates, Mycorrhizae, pH, Soil organic carbon

Synergistic interplay between arbuscular mycorrhizal fungi and fern manure compost tea suppresses common tomato phytopathogens and pest attacks on-farm

Actually, there are intensive efforts towards eco-friendly integrated agricultural management measures to control plant diseases and pests. One of the most promising approaches is the use of arbuscular mycorrhizal fungi (AMF) in combination with organic biopesticides such as eagle fern manure (FM) compost tea. However, their effects have been mainly studied independently from each other. The potential interactions between belowground plant-associated microorganisms such as AMF and aboveground foliar application of biopesticide to mitigate common tomato phytopathogens and pests remain untapped, particularly under on-farm conditions. In a randomized complete block design, the impact of inoculating tomato seedlings with a selected AMF consortium and beyond that the impact of mycorrhized plants receiving three different doses of FM compost tea (0%, 5%, and 10%) on the control of tomato-specific plant diseases and pests and subsequently on the crop yield were examined. The present study demonstrated a sevenfold increase in the rate of mycorrhizal root colonization (from 10% to 70%) in tomato plants that received the combined application of AMF and 10% FM compost tea compared to the control plants that did not receive AMF inoculum and FM compost tea. The combination of AMF and FM compost tea application led to positive synergistic effects that promoted beneficial effects in suppressing the incidence and severity of common tomato diseases and pests. The magnitude of these synergistic effects increased with AMF inoculation and FM compost tea dosage, culminating in greater suppression of tomato plant diseases and pests and, moreover, in an increase in fruit yield compared to control plants. The combination of AMF and 10% FM compost tea revealed a higher suppressive ability against most pathogens and insect attacks. This was evidenced by a 71.3% and 94.7% total reduction in incidence and severity, respectively, compared to control plants. This is the first time that pre-inoculation of AM, combined with FM compost tea application, has been reported as a potential biocontrol alternative to suppress common tomato pathogens and pests while increasing cherry tomato yields sustainably.

Attenuation of Zucchini mosaic virus disease in cucumber plants by mycorrhizal symbiosis

Key messageArbuscular mycorrhizal fungi generated systemic acquired resistance in cucumber to Zucchini yellow mosaic virus, indicating their prospective application in the soil as a sustainable, environmentally friendly approach to inhibit the spread of pathogens.The wide spread of plant pathogens affects the whole world, causing several plant diseases and threatening national food security as it disrupts the quantity and quality of economically important crops. Recently, environmentally acceptable mitigating practices have been required for sustainable agriculture, restricting the use of chemical fertilizers in agricultural areas. Herein, the biological control of Zucchini yellow mosaic virus (ZYMV) in cucumber (Cucumis sativus L.) plants using arbuscular mycorrhizal (AM) fungi was investigated. Compared to control plants, ZYMV-infected plants displayed high disease incidence (DI) and severity (DS) with various symptoms, including severe yellow mosaic, mottling and green blisters of leaves. However, AM fungal inoculation exhibited 50% inhibition for these symptoms and limited DS to 26% as compared to non-colonized ones. The detection of ZYMV by the Enzyme-Linked Immunosorbent Assay technique exhibited a significant reduction in AM-inoculated plants (5.23-fold) compared with non-colonized ones. Besides, mycorrhizal root colonization (F%) was slightly reduced by ZYMV infection. ZYMV infection decreased all growth parameters and pigment fractions and increased the malondialdehyde (MDA) content, however, these parameters were significantly enhanced and the MDA content was decreased by AM fungal colonization. Also, the protein, proline and antioxidant enzymes (POX and CAT) were increased with ZYMV infection with more enhancements due to AM root colonization. Remarkably, defence pathogenesis-related (PR) genes such as PR-a, PR-b, and PR-10 were quickly expressed in response to AM treatment. Our findings demonstrated the beneficial function of AM fungi in triggering the plant defence against ZYMV as they caused systemic acquired resistance in cucumber plants and supported their potential use in the soil as an environment-friendly method of hindering the spread of pathogenic microorganisms sustainably.

Diversity of Mycorrhizal Fungi in Temperate Orchid Species: Comparison of Culture-Dependent and Culture-Independent Methods.

Many orchid species are endangered due to anthropogenic pressures such as habitat destruction and overharvesting, meanwhile, all orchids rely on orchid mycorrhizal fungi (OMF) for seed germination and seedling growth. Therefore, a better understanding of this intimate association is crucial for orchid conservation. Isolation and identification of OMF remain challenging as many fungi are unculturable. In our study, we tested the efficiency of both culture-dependent and culture-independent methods to describe OMF diversity in multiple temperate orchids and assessed any phylogenetic patterns in cultivability. The culture-dependent method involved the cultivation and identification of single pelotons (intracellular hyphal coils), while the culture-independent method used next-generation sequencing (NGS) to identify root-associated fungal communities. We found that most orchid species were associated with multiple fungi, and the orchid host had a greater impact than locality on the variability in fungal communities. The culture-independent method revealed greater fungal diversity than the culture-dependent one, but despite the lower detection, the isolated fungal strains were the most abundant OMF in adult roots. Additionally, the abundance of NGS reads of cultured OTUs was correlated with the extent of mycorrhizal root colonization in orchid plants. Finally, this limited-scale study tentatively suggests that the cultivability character of OMF may be randomly distributed along the phylogenetic trees of the rhizoctonian families.

Timing of connection to mycorrhizal networks matters: Nutrition, N fixation, and transfer of fixed N in maize-bean intercropping

The mycorrhiza-mediated transfer of nutrients to plants connected through mycorrhizal networks may be managed through the timing at which plants integrate to the networks and the integrity of those networks. This is particularly relevant for intercropping agrosystems. We used soil tillage to disrupt mycorrhizal networks and sowing time treatments to manipulate the connection time of maize and bean in a field experiment. We hypothesized that 1) the benefits from connecting to mycorrhizal networks would be greater for the crop that is established first and retrieved resources from the network without competition, and 2) tillage disruption delaying colonization and connection to preserved mycorrhizal networks would reduce mycorrhizal colonization in roots and soil, crop nutrition, N fixation by beans, and transfer of fixed N to maize. Mycorrhizal network disruption with tillage reduced early mycorrhizal development in roots and soil, and N and P nutrition of both crops. In general, sowing time had no effect in maize but tillage increased plant density, growth, and the yield of maize by alleviating soil compaction. Reduced tillage and early sowing increased nutrition, development, N fixation and yield of bean. N derived from symbiotic fixation in bean and transferred to maize were higher with bean sown before maize under reduced tillage. Early connection to mycorrhizal networks favored mostly bean and made little difference to maize regardless of sowing time, contrary to our expectations. The greatest overall benefit for both crops was obtained when bean was sown before maize and connected early to preserved mycorrhizal networks under reduced tillage.

Defense responses and symbiotic functional initiation in trifoliate orange‒arbuscular mycorrhizal fungi interaction

Arbuscular mycorrhizal fungi (AMF) trigger beneficial effects on their hosts, but it is unknown how plants modulate their defense responses during root colonization of AMF and the symbiotic benefits are initiated. The purpose of this study was to analyze the root mycorrhizal colonization process of trifoliate orange and the responsive patterns of plant growth, root peroxide hydrogen (H2O2), antioxidant enzymes and their encoding gene expression, and sugar, lipid and phosphate transporter protein gene expression at 7‒56 days of inoculation (doi) with Funneliformis mosseae (Fm). Fm developed appressoriums on the root surface at 7 doi, followed by abundant arbuscules in root cortical cells at 28 doi, intracellular vesicles at 42 doi, and root mycorrhizal colonization rate of 41.54% at 56 doi. Plant growth improvement by Fm started at 28 doi. The immune defense response of roots was initiated at 7 doi, as evidenced by the increase of H2O2 levels and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity, as well as the up-regulation of PtMn-SOD, PtCu/Zn-SOD, PtPOD, and PtCAT expression, which lasted until 14 doi. Starting at 28 doi, a sugar transporter gene (PtSWEET), a lipid transporter gene (PtSTR), and a phosphate transporter gene (PtPT6) were initiated to be up-regulated, followed by the up-regulation of PtSTR2, PtPT3, and PtPT5 at 42 doi and PtFe-SOD at 56 doi. Arbuscule formation and plant growth improvement together at 28 doi suggested that arbuscules trigger improved growth responses of host plants. This study also reveals the initiation of host immune defense response and function in early root AMF colonization.Graphical

Micorrizas arbusculares em pomares de mangueira no semiárido brasileiro: influência da fenologia, do manejo e da variedade

ABSTRACT: Arbuscular mycorrhizal fungi (AMF) increase the absorption surface of roots, providing greater absorption of water and nutrients from the soil by plants. Thus, it is important to know how arbuscular mycorrhizae are affected by factors such as phenology, management and varieties in mango (Mangifera indica) orchards in the irrigated semi-arid region. With this objective, soil and root samples were collected during the vegetative, flowering and fruiting stages, and in the water stress period before flowering, always on the same trees. The study was carried out in mango orchards of the Keitt and Palmer varieties, in agricultural farms located in Juazeiro - BA and Petrolina - PE, both under conventional management (with fertilizers and paclobutazol). The soil was used to quantify the number of AMF spores and phosphorus content. Mycorrhizal colonization in roots was evaluated in qualitative terms (presence of hyphae, vesicles and arbuscles) and quantitative terms (% of colonization). Total mycorrhizal colonization was high, with averages above 65%, and higher values in the fruiting period. Colonization by vesicles and arbuscles was on average above 45% and 17%, respectively, with higher means also during fruiting. The number of AMF spores in the soil averaged over 130 spores in 50 g of soil, with higher values in the period of water stress. The phosphorus content in the soil did not influence mycorrhizal colonization and the number of spores in the soil. The association of AMF with mango trees was generally affected by management and phenology, regardless of the cultivated varieties.

Arbuscular Mycorrhizal Fungi, Especially Rhizophagus intraradices as a Biostimulant, Improve Plant Growth and Root Columbin Levels in Tinospora sagittata

Tinospora sagittata is a columbin-rich medicinal plant, but its columbin levels are reduced under artificial cultivation conditions. The objective of this study was to analyze the effects of inoculations with Diversispora versiformis (Dv), Funneliformis mosseae (Fm), Rhizophagus intraradices (Ri), and mixed inoculation (Dv + Fm + Ri) (Mix) on growth performance, root morphology, leaf photosynthetic physiology, and root columbin levels in T. sagittata. These arbuscular mycorrhizal fungi (AMF) were able to colonize the roots, as evidenced by a root mycorrhizal colonization rate ranging from 17% to 48% and soil hyphal lengths ranging from 17.51 cm/g to 32.02 cm/g, with the Mix treatment being the greatest. AMF inoculations improved plant height (16–151%), leaf number (119–283%), shoot (37–211%), and root biomass (22–318%) to varying extents, with Ri and Mix treatments being the most prominent. AMF-treated plants presented relatively greater root total length, projected area, surface area, volume, and average diameter, especially those treated with Ri and Mix. AMF inoculations also significantly improved the leaf nitrogen balance index, transpiration rate, and stomatal conductance, while the photosynthesis rate and chlorophyll index varied by AMF species, along with a decrease in intercellular CO2 levels. Root columbin levels ranged from 0.524 mg/g to 5.389 mg/g, and AMF inoculation significantly increased root columbin levels by 228–928%, with Ri being the most significant. Root columbin levels were significantly positively correlated with soil hyphal length, root total length, root projected area, root surface area, root volume, and root average diameter, but not root AMF colonization rate. This study demonstrates for the first time that AMF, especially Ri, can be employed as a biostimulant to promote growth as well as root columbin levels in T. sagittata, where AMF-triggered improvement in root morphology is an important reason for promoting root columbin levels.

Positive Changes in Fruit Quality, Leaf Antioxidant Defense System, and Soil Fertility of Beni-Madonna Tangor Citrus (Citrus nanko × C. amakusa) after Field AMF Inoculation

Citrus plants rely heavily on arbuscular mycorrhizal fungi (AMF) due to their lack of root hairs. Most experiments have been conducted with AMF inoculation under potted conditions, while field inoculation of AMF on citrus, especially a high economic hybrid tangor variety Beni-Madonna (Citrus nanko × C. amakusa), has been rarely recorded. This study aimed to analyze the effects of two AMF inoculations (a single Funneliformis mosseae and a mixture of F. mosseae, Diversispora versiformis, and Rhizophagus intraradices) on the internal and external fruit quality, leaf antioxidant defense system, and soil fertility and structure of top-worked Beni-Madonna tangor citrus trees. Three and a half years after AMF inoculations, soil hyphal length and root mycorrhizal colonization rate increased by 61.2–101.8% and 15.85–29.6% in inoculated plants, respectively. Inoculated trees had higher external fruit coloration value, fruit horizontal diameter, and fruit weight, and lower fruit rigidity than uninoculated trees. AMF-inoculated trees had higher glucose levels of fruit peels, fructose and sucrose levels of fruit fleshes, and the ratio of fruit soluble solids/titratable acids, as well as lower titratable acids concentrations than non-AMF-inoculated trees. AMF inoculation significantly increased leaf nitrogen balance index, chlorophyll index, peroxidase, catalase, superoxide dismutase, and glutathione reductase activities, as well as reduced glutathione and oxidized glutathione concentrations, resulting in lower hydrogen peroxide and malondialdehyde levels when compared to the uninoculated treatment. In addition, inoculated trees presented higher soil nutrient levels, including organic carbon, available K, and Olsen-P as, well as soil aggregate stability (based on mean weight diameter) than uninoculated trees. This study concluded that field AMF inoculation improved fruit quality, enhanced leaf antioxidant defense system, and improved soil fertility of Beni-Madonna trees, with mixed AMF being prominent in improving fruit quality and F. mosseae being prominent in enhancing leaf antioxidant defense system and improving soil fertility.

The physiological responses of celery (Apium graveolens L.) and its ability to accumulate selenium when inoculated with Funneliformis mosseae

Celery (Apium graveolens L.) has a strong capacity to enrich selenium (Se) and is a good system for research on Se enrichment in vegetables. Arbuscular mycorrhizal fungi (AMF) are commonly used plant symbionts that affect plant growth and their effectiveness is plant species specific. However, there is little research on the effects of AMF inoculation on the accumulation and translocation of Se in celery. The treatments in this study included inoculation with AMF (+AMF) and the application of different types and concentrations of exogenous Se. We evaluated the growth, root mycorrhizal colonization, photosynthetic pigment content, ascorbate-glutathione cycle (ASA-GSH cycle), the accumulation and translocation of Se and the combination of AMF + Se compared with an untreated control. The application of low concentrations of Se (≤10 mg kg−1) stimulated celery growth, while high concentrations (>20 mg kg−1) had the opposite effect. The inhibition of celery growth was more severe with Se6+ than Se4+ when applied at the same concentration. The accumulation of Se improved in all the organs of celery as the supply increased. AMF had a significant positive effect on the accumulation and translocation of Se. In addition, +AMF significantly increased the shoot height and root fresh weight of celery and reduced the inhibitory effect of Se on growth. However, +AMF had slight effects on the levels of photosynthetic pigments and the ASA-GSH cycle. +AMF combined with 10 mg kg−1 sodium selenite (Se4+) is an effective way to produce Se-rich celery.

Arbuscular Mycorrhizal Fungi Colonization of Jatropha curcas Roots and Its Impact on Growth and Survival under Greenhouse-Induced Hydric Stress

Arbuscular mycorrhizal fungi (AMF) provide benefits to host plants by enhancing nutrition and overall fitness. In this study, AMF species were isolated from the soil rhizosphere of Jatropha curcas and were identified and evaluated for their potential in fostering the development of Jatropha seedlings within a controlled greenhouse environment. The first experiment assessed the interplay between hydric stress and AMF inoculation on mycorrhizal colonization. The next experiment examined the impact of quercetin on mycorrhizal colonization. Out of 204 glomerospores corresponding to 28 species spanning 10 genera, Acaulospora (14) and Scutellospora (5) were the most abundant taxa. Six new records of AMF for Costa Rica are reported. Mycorrhizal colonization was observed in 43.2% of Jatropha plants (34.7% by AMF typical hyphae; arbuscules 8.9%; coils 5.6%; and vesicles 5.4%). Significant survival effects due to AMF inoculation under hydric stress were observed. On day 85, non-mycorrhizal plants subjected to hydric stress showed a mere 30% survival rate, whereas their mycorrhizal counterparts under hydric stress exhibited survival rates of 80% and 100% with and without irrigation, respectively. Furthermore, plants with irrigation and mycorrhizas showed greater hydric stress tolerance and superior growth. The inoculated plants, irrespective of irrigation, demonstrated mycorrhizal colonization rates of 63% and 72%, respectively. Quercetin did not affect Jatropha’s growth, but there were differences in AMF root colonization. In summary, these findings accentuate the viability of a native consortium in augmenting Jatropha survival, warranting consideration as a potent biofertilizer within greenhouse settings. The AMF described can be used for Jatropha propagation programs.

Higher colonization but lower diversity of root-associated arbuscular mycorrhizal fungi in the topsoil than in deep soil

Arbuscular mycorrhizal fungi (AMF) colonizing plant roots play a pivotal role in maintaining soil nutrient cycling and ecosystem stability, and this role may vary in different habitat environments. However, the influence of soil depth on root AMF colonization, diversity, and the complex interactions among AMF taxa is still not well understood. In this study, we investigated the frequency, intensity, and abundance of root AMF colonization, as well as root AMF diversity, composition, and co-occurrence patterns across three soil depths: 0–20 cm, 20–40 cm, and the soil-rock mixing layer. Soil nutrients (e.g., organic matter, nitrogen, and phosphorus) and root biomass were higher in the 0–20 cm layer than in the soil-rock mixing layer, while soil pH showed an opposite relationship. The higher root biomass in the upper soil layer may enhance root secretions and exudates, thereby promoting root AMF colonization. In contrast, the lower soil nutrient content and higher soil pH observed in the 20–40 cm and soil-rock mixing layers may contribute to greater AMF diversity in the deeper soil layers compared to the topsoil. Although no significant differences were observed in the composition of the root AMF community, specific amplicon sequence variants affiliated with Glomus, Racocetra, and unclassified taxa were more enriched in the 20–40 cm and soil-rock mixing layers compared to the 0–20 cm layer. Network analysis revealed that deep soil, compared to topsoil, enhances interactions among root AMF by intensifying competitive relationships. This suggests that the complex interactions among root AMF taxa within deep soil contribute to the resilience of root AMF in resource-scarce conditions, particularly in the 20–40 cm layer and the soil-rock mixing layer. At the genus level, Glomus, Racocetra, and unclassified taxa emerged as keystone taxa due to their prominent linkage with other root AMF groups. Collectively, the results suggest that higher soil nutrient levels and root biomass can promote root mycorrhizal colonization but suppress AMF diversity and weaken interactions among root AMF taxa in the upper soil layer compared to deeper soil layers. Furthermore, the distinct functions of AMF colonization and diversity at different soil depths should be considered when evaluating vegetation reconstruction in karst ecosystems with varied soil depth distribution.

Response to side-banded phosphorus and zinc fertilizer for corn grown after canola or soybean in southern Manitoba

A 2-year crop rotation study in southern Manitoba assessed the effects of starter fertilizer on grain corn ( Zea mays L.) production when corn followed canola ( Brassica napus L.) versus soybean ( Glycine max L. Merr.). Treatments included a control (no starter) and two rates of phosphorus (P) (30 and 60 kg P2O5 ha−1) as monoammonium phosphate (MAP, 11–52–0) or MicroEssentials® SZ (MESZn, 12–40–0–10–1) side-banded at planting. The preceding crop did not have any influence on mycorrhizal colonization of corn roots at the V4 corn growth stage. However, side-banded fertilizer increased early-season biomass by as much as 111% compared to the unfertilized control, averaged across all site-years, with the largest increases occurring where corn followed canola. P concentration and uptake in early-season biomass increased as the P rate increased. Zinc (Zn) concentrations in early-season biomass were the greatest for the unfertilized control and MESZn treatments, while Zn uptake was significantly greater with the application of starter fertilizer compared to the unfertilized control. Starter P advanced silking date by 2–7 days relative to the unfertilized control. At maturity, starter P reduced grain moisture by 21–27 g kg−1 in corn only after canola. The high rate of MAP increased grain yield by an average of 770 kg ha−1 compared to the unfertilized control, regardless of the preceding crop. The negative influence of the preceding canola crop on early-season growth and mid-season development of corn can be managed with starter fertilization to provide adequate P and Zn to the corn crop and maintain successful production in Manitoba.

Co-application of arbuscular mycorrhizal fungi and nano-ZnFe2O4 improves primary metabolites, enzymes and NPK status of pea (Pisum sativum L.) plants

Nowadays, a strong ascending interest is given to the use of nanoparticles in soils to evaluate their benefits or risks to plants and microbes. Pea (Pisum sativum L.) of the family Fabaceae is among the crops cultivated by farmers in the winter season. From here, this study was conducted to examine the impact of arbuscular mycorrhizal fungus (AMF) and zinc ferrite nanoparticles (nano-ZnFe2O4) co-application on biochemical parameters and mineral contents of pea plants, as well as the impact of nano-ZnFe2O4 application on mycorrhizal root colonization. For this purpose, nano-ZnFe2O4 with a crystallite size of 25.4 nm was used in two different concentrations (0 and 5 µM) in pots planted with pea plants and inoculated or non-inoculated with AMF. The results showed that nano-ZnFe2O4 to some extent inhibited AMF colonization of pea plant roots. Additionally, in comparison to non-AM controls, the combined use of AMF and nano-ZnFe2O4 was successful in raising the activity of helpful enzymes (acid phosphatase, alkaline phosphatase, catalase and peroxidase) as well as biochemical parameters including primary metabolites (carbohydrates, protein, and amino acids). Moreover, an improvement in mineral nutrients uptakes in pea plants such as N, P, K and Mg appeared in the combined treatment. Therefore, nano-ZnFe2O4 coupled with AMF promises potential applications in agriculture because Zn and Fe are two essential micronutrients that need to be supplied to crop plants.